This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Applications 100 27 314.9, filed on Jun. 5, 2000; and 100 46 004.6, filed on Sep. 18, 2000, the entire disclosures of which are incorporated herein by reference.
The invention relates to an aircraft door with a framework clad by an outer skin connected to the framework. The invention also relates to a molding or casting tool for casting the aircraft door.
It is known to cast, including sand casting, aircraft doors, see xe2x80x9cTechnical Data Sheetxe2x80x9d: Aluvic Hitchcock International of 1997. Casting and structural details are not disclosed in the xe2x80x9cTechnical Data Sheetxe2x80x9d.
Sand casting molds generally include a top part, a bottom part and cores which together determine the shape of the aircraft door structure. The cast aircraft door structure includes an outer skin and a framework, both of which are formed integrally by the casting.
An aircraft door essentially comprises an outer skin attached to a framework. When the aircraft door is closed, the outer skin extends flush with the surrounding surface contour of the fuselage skin. The outer skin of the door is stiffened by the door framework. The framework may include beams extending in parallel to the longitudinal central axis of the fuselage, as is characteristic for example for a passenger door, and/or the door may include ribs extending in a circumferential direction relative to the longitudinal central axis of the fuselage, as is for example characteristic for a freight door of an aircraft. During flight, the framework in particular takes up loads and transfers the loads to the fuselage.
Handling devices are also accommodated in and attached to the door framework, including controllable mechanical and electrical subassemblies, at least for opening and closing the door. As a rule, an aircraft door is connected to the frame of the fuselage by means of a hinge or a joint arrangement. These features apply both to passenger doors and to freight doors. Therefore, the term xe2x80x9cdoorxe2x80x9d as used herein is intended to refer to passenger doors and freight doors alike.
Generally, distinctions made between passenger doors and freight doors in aircraft engineering are based upon different functions and on construction differences between passenger doors and freight doors. In the case of a passenger door, the load bearing direction is aligned along the fuselage length, more specifically the loads extend substantially in parallel to the longitudinal central aircraft axis. Thus, carriers referred to as xe2x80x9cbeamsxe2x80x9d herein are preferably used in the framework of a passenger door. In the case of a freight door, the load bearing direction is effective in a circumferential direction around the fuselage relative to the longitudinal central aircraft axis. Therefore preferably ribs are used in the framework of a freight door.
Conventionally, the production of an aircraft door takes place in various steps. One step involves producing the framework, with the beams or ribs being spaced apart by individual frame sections secured to the beams or ribs. The outer skin is then connected to the framework by rivets, by a known riveting method, as for example disclosed in U.S. Pat. No. 4,662,556. The riveting operation is relatively time consuming and expensive.
In view of the above it is the aim of the invention to achieve the following objects singly or in combination:
to produce an aircraft door by using production steps that are considerably more economical, compared for example to riveting steps or adhesive bonding steps;
to form an aircraft door made with its skin and framework as a single integral piece in one casting operation;
to optimally simplify the door framework, so that its integral casting together with the door skin is possible with a correspondingly simple casting mold and core; and
to construct the mold so that at the most it requires but one single core per beam or rib of the framework, and so that the number of needed core types is minimized.
According to the invention there is provided a cast aircraft door comprising an inner framework and an outer skin integrally connected to said inner framework by a casting operation, said inner framework comprising frame elements, each frame element having at least one arched frame section, wherein each frame section comprises a plurality of arches and a bridge portion bridging said plurality of arches, said frame element further comprises a cavity in said at least one arched frame section.
According to the invention there is further provided a combination of a mold and core assembly for casting an aircraft door having an inner framework covered by an outer skin integrally secured to said inner framework by simultaneously casting in said mold, said inner framework and said outer skin, said inner framework comprising a plurality of frame elements arranged in parallel to each other, said mold comprising a first mold part and a second mold part and said core assembly consisting of a single core for each frame element.
The present aircraft door avoids in its frame structure numerous undercuts or back tapers so that complicated negative molds and cores for casting these back tapers are also avoided. The production of complicated negative molds is very time-consuming and expensive. The invention avoids using such complicated molds.
In order to cast a beam or rib of an inner aircraft door framework, at the most one core is required for each rib or beam, according to the invention. This is optimal, for it makes possible a fast casting production. The invention avoids the use of a plurality of cores for each rib or beam. Making many cores again and again, inserting and positioning these many cores in the mold prior to casting, is time-consuming and would not allow any significant increase in the rate of door production. The invention overcomes such obstacles in that it provides an advantageous mold with cores of efficient production configurations, whereby only one core is required for each beam or rib and the number of core types or different core shapes is four at the most.
The entire core assembly for casting a passenger door according to the invention is formed by a plurality of individual cores, one of which is provided for each frame element of the door frame to be cast. Each individual core of a first core type has a longitudinal land with cross stubs arranged crosswise to said longitudinal land which essentially corresponds to the length or width of the door, whereby the door length is measured in the circumferential direction and the door width is measured in the axial direction of the aircraft, more specifically the central, longitudinal aircraft axis. Each core has cross stubs spaced apart from each other. The length of a cross stub corresponds to the length of the spacing between two mold markers provided in at least one of the mold parts. When producing a passenger door with beams, for example the respective cores are positioned side-by-side in the mold to extend in the axial direction while spacing the cores from one another in the circumferential direction. The cross-section of the core perpendicularly to the length of the core is trapezoidal. Thus, the cores have an incline that simplifies removing the cast door from the mold.
A preferred door embodiment made by casting is characterized in that the cross-section of the beams and/or ribs of the inner door framework integrally connected to the outer skin, comprise a cavity which is trapezoidal in its cross-section. The trapezoidal cross-section has two parallel sides, one of which is shorter than the other, whereby the longer side is formed by the outer skin. This construction applies to both passenger doors and freight doors. Additionally, the outer skin is stiffened by stiffeners formed or molded on the inwardly facing surface of the outer skin.
These stiffeners are formed on the inside of the outer skin in particular in those places where planes of separation between cores and/or between the top part of the mold and the bottom part of the mold, are arranged. During casting of a freight door, cores are insertable in the mold which at most belong to four different types of cores. In this way, optimally low production costs are achieved by minimizing the number of cores and the core types. Further, by constructing each inner door frame element forming a rib or beam as at least one, preferably two frame sections, the door frame and accordingly each single core for each frame element has a simple configuration or shape, which facilitates the core production and the removal of the finished cast from the mold.
The invention results in clear advantages. Compared to a conventional mold requiring a plurality of cores for each beam or rib, the invention uses at the most one core per beam or per rib. In this way, relatively few cores need to be inserted in the mold. This feature results in reduced production costs because of significant time savings in the production of the present cores compared to the production of a door made by conventional casting methods. In this way, an acceptable mass production becomes possible. Since there are no back tapers, a relatively simple negative mold of the aircraft door is used. The inner segments between beams or ribs and the inner skin surfaces, hitherto required in the case of known doors, have also been avoided by the invention.